Fluid-operated continuously actuated reciprocating piston drive



United States Patent abandoned Nov. 17, 1970 [72] inventor [45] Patented [32] Priority May 20, 1965 [33] Germany [31] St 23,856

[54] FLUID-OPERATED CONTINUOUSLY ACTUATED RECIPROCATING PISTON DRIVE 8 Claims, 8 Drawing Figs.

[52] U.S.Cl 91/306, 9l/309,91/3l3,9l/3l7, 91/319 [51] Int. Cl l. F01l25/06 [50] Field ofSearch 91/306,

305(Cursory), 304 l(Cursory). 301 (Cursory), 309, 3 l3(Curs0ry) 3 l 7(Curs0ry) 3 19(Cursory) [56] References Cited UNITED STATES PATENTS 553,261 III 896 Reussner 91/309 688,598 12/1901 Caryell 91/306 Primary Examiner Paul E. Maslousky Attorney-John J. Dennemeyer ABSTRACT: A double-acting pressure booster having at least one reversing valve for reversing the pressure medium towards one or the other side of the low pressure piston wherein the reversing valve is reversed by a pressure difference created by the movements of the low pressure piston. The slide member ofthe reversing valve has at least one two-step control surface, one surface of which is without effect in one end position of the slide member due to being sealed offand the other surface is constantly subjected to the pressure medium while the slide member is maintained in the end position by a greater counterforce. During the reversing action the sealed-off control surface is connected up suddenly after an initially delayed movement of the slide member so that the valve is reversed positively also during the creeping movement of the low pressure piston.

Patented Nov. 17, 1970 3,540,349

Sheet 1 of3 INVENTOR. HERMANN J. PENNTHER Patented Nov. 17, 1970 3,540,349

Sheet 2 of3 Patented Nov. 17, 1970 3,540,349

Sheet 3 of3 FLUID-OPERATED CONTINUOUSLY AC'IUATEI) RECIPROCATING PISTON DRIVE This is a division of US. Pat. application Ser. No. 558,176, filed May 17, 1966, now abandoned.

This invention relates to a hydraulically or pneumatically actuated piston drive with a reciprocating movement, and more particularly to a double-acting booster in which the movements of the low-pressure piston influence in the end positions the control pressure for the reverse operation. Although the invention is not limited to pressure boosters but may be applied in a similar manner to most embodiments, for example also for hydraulically or pneumatically actuated mtors; the following description will be limited to double acting pressure boosters.

In the field ofthe double-acting air compression motors it is known for the reverse operation, that the movements of the work piston reduce in the end positions the control pressure of an impulse regulator, [.0. of a four-way valve regulated, by pressure release, into whose regulation chambers disposed on both sides of the control slide and in contact with the pressure source the control lines open.

In another type of air compression motor the usual threeway pilot valves which are mechanically actuated by the work piston and which regulate the four-way valve have been replaced by simple two-way pilot valves so that the constant pressure impingement in the two regulation chambers of the four way valve is provided by auxiliary bores in the control slide or in the valve body of the four-way valve instead of by the three-way pilot valves. The bores connect the pressure source to the two regulation chambers.

This arrangement has the disadvantage that it fails in case of a creeping travel ofthe work piston. The reason for this is that during very slow travel the pilot valves also open very slowly so that the pressure release of the control chambers takes place very slowly in the end positions so that the control slide starts to travel slowly into the opposite end position and stops in its travel in the center position because the pressure difference is not sufficient to overcome the further resistance to its movement. Depending on the construction ofthe valve a) The pressure connection and both cylinder connections are closed offor b) the pressure connection is closed off and both cylinder connections are without pressure.

The lowpressure piston remains stationary and the pilot valves remain in the degree of aperture in which they happen to be at that moment.

It is an object of the present invention to provide for in a continuous piston drive of the above-mentioned type a reversing delay by simple connecting means which, similar to the known quick break connection or throttling in control lines, prevents a stopping of the piston drive during creeping travel but which on the other hand does not impede the rapid travel which can occur by a throttling in a control line.

The invention provides a solution which includes for the reverse operation ofthe actuating pressure in a known manner an impulse-controlled four-way valve.

According to the invention the bores provided in the valve covers of the four-way valve are constantly open at least in the end positions of the control slide and that the two face sides of the control slide each present control surfaces located in different planes. In the end positions the first control surface is connected by a throttled line with the pressure source as well as with the outgoing control line and the other remaining control surface is relieved by the bore in the valve cover and is subject to a sealing action to the first control surface. The sealing is effective over a limited, ineffective partial movement of the reversed control slide.

The reversing retardation takes place upon a pressure release on the side of the control slide which had been receiving the full impingement. A movement of the control slide is started only after a predetermined pressure drop because, on the other side, only a portion of the control surface, namely the first control surface, is being impinged, the remaining surface being relieved. When the movement ofthe control slide is initiated, the remaining surface is lifted from the sealing position whereby it is additionally impinged upon, and a sudden power difference between opposite total control surfaces is created which reverses the control suddenly.

It is essential that in the end positions of the control slide of the four-way valve partial surfaces ofthe face side control surfaces are initially relieved but, after a short return travel, receive the additional impingement.

The arrangement ofthe reversing valves according to the invention makes possible simplifications in the manner in which the changes of the control pressure are initiated by the movement ofthe work piston ofthe piston drive.

These simplifications will be explained hereafter in greater detail with reference to the attached drawings in which the invention is illustrated by means of diagrams showing several embodiments of double-acting hydraulic pressure boosters and in which:

FIGS. 1,2,4 and 5 are circuit diagrams including a four-way valve; 5

FIG. 3 according to FIG. 2 shows a detail view of a modification to the circuit diagram;

FIGS. 6 and 8 show sections of the four-way valve,

FIG. 7 shows a circuit symbol ofthe four-way valve.

The continuous piston drive, shown in the embodiments, as hydraulic, double-acting boosters, consists in a known manner according to FIG. I ofa low-pressure cylinder in which the work piston 21 divides the cylinder into two work chambers 22 and 23, the high-pressure cylinders 24, 25 and the highpressure pistons 26, 27 which represent the piston rods in a motor drive. The high pressure is introduced alternately through check valves 28, 29 in the lines 30, 31 to the consumer station. Through check valves 32, 33 in the lines 34, 35 the high-pressure pistons 26,27 may take up pressure medium during their return strokes. The lines 34, 35 are connected with a four-way valve 36 (FIGS. I, 2, 4 and 5) alternately to the pressure line 39 or the return line 40 to the reservoir 41. Over the branches 42, 43 the work chambers 22 and 23 of the low pressure cylinder 20 are alternately impinged and connected to the return flow. In this respect all the circuits are the same. Furthermore the condition ofthe individual chambers is indicated in all these circuits by reference letter p or o to indicate that they have a positive pressure p or a zero pressure a.

Reference is now made to FIGS. 6 and 8 to show the arrangement according to the invention on the four-way valve 36. The control slide 45 has at its face surfaces on both sides central pistonlike projections 45a each with a surface F designated as the abutment surface, located in front of the remaining circular surface of the first control surface F,. Very small bores 46, 47 are provided in the valve covers I37, I38 which according to FIG. 6, are constantly without pressure, and according to FIG. 8 they are without pressure only in the end positions ofthe control slide 45.

In the two covers of the valve body (or valve covers) 137, 138 annular rubber seals 48, 49 are disposed which cover one abutment surface F, of the control slide 45 in each end position thereof the space inside the seals is vented to the outside through the bores 46, or 47.

The control chambers 50, 51 at opposite sides of the slide 45 are connected constantly to the inlet or the pressure line 39 over auxiliary bores 52, 53 in the control slide. In FIGS. 6 and 8 the control surfaces F, and F, of the left side are entirely exposed to the pressure while through the small bore 46 only a small amount of pressure medium escapes. However, on the right side only the first control surface F, is exposed to the pressure as the abutment surface F is sealed off by the elastic annular seal 49 and relieved. In this way the control slide 45 has a stable end position because the force p, (F, F coming from the left is opposed by the counter force p. F, coming from the right.

Referring to the embodiment according to FIG. I it will now be explained in what manner a pressure difference can be created in the two control chambers 50 and 51. As long as the pilot valves 63, 64 are closed, no fluid flow occurs through control lines 61, 62. Thus indentical pressures (P) are built up in the spaces 50 and 51 which communicate with the pressure source via the bores 52, 53. As already explained, the forces acting on the slide 45 are different due to the lack of pressure on abutment surface F As the working piston 21 arrives at its left end position it actuates the ram 65 which opens the pilot valve 63. Thus pressure in the control chamber 50 is reduced since the pressure medium may now flow from the control chamber 50, through the control line 61, through the now open pilot valve 63 and then to a reservoir 41 or pressure free chamber. This and other means for relieving pressure from the control chambers ofthe four-way valve are more fully described later herein.

When, as above, the pressure on the left is reduced, there is an initial, incremental return movement ofthe control slide 45 corresponding to the elastic return of the annular seal 49. At the moment where the pressure has dropped below the value abutment surface F is then released from the sealing contact with the annular seal subjecting this surface to pressure impingement which creates an additional displacement force a the right, causing a sudden displacement of the control slide 45 into the opposite end position. The available displacement force increases thus exactly the same as the displacement resistance proportional to the working pressure p. In this connnection it is also favorable that the sealing rings 48, 49 reduce in the end positions the speed of the control slide without shock to the value 0.

Fig. 6 shows thus a possible embodiment of the four-way valve 36 controlled by pressure relief impulses with reverse operation delay by pressure relieving the abutment surfaces F, by means of the small bores 46, 47 in the valve covers (137, 138). FIG. 8 shows an embodiment in which the pressure relief of the surfaces F is produced by the control slide 45 and wherein with full exposure of the surfaces F and F for example the bore 46 is closed off through line 54 to avoid a leakage flow. Both embodiments are illustrated by the circuit symbol according to FIG. 7 in which the forces retarding the reverse operation are indicated by arrow points. The auxiliary bores 52, 53 in the control slide 45 are replaced here by dash lines with built-in throttles 55, 56.

Referring back to FIG. 1 the two-way pilot valves 63, 64 built into the control lines 60, 61 serve to produce the pressure relief impulses for reversing the four-way valve 36. The two-way pilot valves are closed in the rest position by spring power means 163, 164 and mechanically opened in the end positions by the work piston 21 ofthe piston drive by means of rams 65, 66 wherein the pressure relief of the control chambers 50, 51 of the four-way valve is directed into the outer chamber which has no pressure or into the reservoir 41.

In the circuit according to FIG. 1 a further simplification is possible which consists in that instead of the control pressure of the four-way valve 36 being discharged directly into the reservoir or into the pressure-free chamber, it may be p. the reverse operation begins. The

discharged into work chambers 23 or 22 when they are free of pressure. This is possible because the operating pressure p penetrating into these work chambers after completed reverse operation can no longer cancel the reverse operation because the control chamber of the four-way valve located on the opposite side is closed off so that also no impulse effect can arise. Thus it is possible, as may be seen in FIG. 4, to replace the three-way pilot valves by simple springbiased check valves 67, 68 which are pushed open in the end positions by the lowpressure piston 21 and which, after completed reverse operation, are closed by the spring pressure. If one wishes to employ the high-pressure pistons 26, 27 also for the reverse operation the circuit according to FIG. I may be simplified by providing, as shown in FIG. 2, two diametrical bores 69 and 70 through each of the two high-pressure cylinder housings, the set of each, the bores 69 being connected to the left or right control chamber 50, 51 of the four-way valve, the bores 70 being connected with the reservoir 41 or the pressure-free outer chamber.

Each high pressure piston is provided with an annular groove 71, 72 which in the left or right end position connects the bores 69 and 70 whereby the control chambers of the fourway valve are relieved of pressure and the reverse operation is initiated. Since through the bores 69 a one-sided pressure is exerted on the high-pressure pistons, this solution is advisable only for compressed air drives because here the pressure lies mostly under 10 kg./cm Since the diameter of the bores 69 is small and since, with a horizontal disposition of the booster, the weight of highand low-pressure pistons acts downwardly, the forces are partly compensated. The one-sided pressure on the high-pressure pistons may be avoided if one provides instead of the bores 69 and 70 according to FIG. 3 adjacently disposed annular chambers 73, 74 which in the end positions are connected to each other by correspondingly wider annular grooves 71, 72 or longitudinal grooves 75 in the high-pressure pistons 26, 27.

In the same manner the circuit according to FIG. 4 may be simplified by again employing the high-pressure pistons 26, 27 for the reverse operation. As shown in FIG. 5, control lines 61, 62 of the four-way valve 36 are connected on both sides with annular chambers 78, 79 in the cylinder housing which surround the high-pressure pistons 26, 27. The annular chambers 78, 79 are open toward the end of the stroke of the work piston since the areas or recesses 80, 81 of the highpressure pistons 26, 27 move into the annular chambers 78, 79 and establish the connection to the work chamber 23 or 22 which is free of pressure, whereby the reverse operation of the four way valve 36 is obtained.

The measures described according to FIGS. 2 to 5 for replacing the pilot slides 63, 64 may also be employed independently of the reversing delay according to the invention when this delay is not required with a sufficiently rapid travel ofthe pressure booster.

It is pointed out further that one can connect or disconnect the booster in a simple manner by opening and closing a through valve (not shown) which is built into one of the two control lines 61,62.

If one compares the end results of the first operating system, namely the circuits according to FIGS. 2 to 5, with the starting position according to FIG. 1 the improvement obtained is clearly visible. Besides the reversing delay which is obtained the circuit is substantially simplified, the pilot valves are completely eliminated and with them all forces which act excentrically on the differential piston. Due to the elimination of the springs the operating safety is also increased. As driving medium in the circuit according to FIG. 5 pressurized gas as well as pressurized fluid are equally suitable while the circuit according to FIG. 2 is suited only for a drive with pressure gas.

I claim:

1. A fluidoperated continuously actuated reversing piston drive with reciprocating movement comprising: a work piston movable between two ends of a cylinder having a pair of work chambers for controlling pressure of an impulse-controlled four-way valve having a control slide and control chambers on opposite sides thereof; control lines communicating with said control chambers; said four-way valve communicating with a pair of branch means for alternately delivering a pressure medium to one of said work chambers; said control slide having two end positions, one of said branch means being connected with a pressure line means in each of said two end positions for transmitting working pressure to one of said work chambers of said piston drive, the other of said branch means being connected in the same end position of said control slide to a return line via said four-way valve; said four-way valve having a pair of valve covers at each end thereof; said control slide having a pair of face sides each having a first control surface and an abutment surface located in different planes, said first control surface being continuously exposed to said working pressure, said abutment surface being in sealing cooperation with one of said two valve covers in each of said end positions; and pilot means being actuated by the movement of said work piston for effecting a pressure drop in one ofsaid control chambers and thus a pressure relief impulse causing at least a delayed movement of said control slide toward said one of said control chambers with the pressure drop, said first control surface in the other of said control chambers being exposed to said working pressure, said abutment surface in said other of said control chambers being suddenly effectively added to said first control surface for forcing said control slide into the other of said two end positions.

2. A piston drive as defined in claim 1 further including auxiliary bore means in said control slide for continuously transmitting pressure from said pressure line means to said control chambers of said four-way valve and said control lines.

3. A piston drive as defined in claim 1 further including a small bore in each of said valve covers for relieving pressure from said'abutment surfaces of said control slide when in sealing cooperation with said valve covers.

4. A piston drive as defined in claim 1 further including central, pistonlike projections on each of said face sides, said abutment surfaces of said control slide being formed on said central, pistonlike projections, and elastic annular seals mounted in said valve covers.

7. A piston drive as defined in claim 1 further including spring-biased check valves between said control lines and said work chambers.

8. A piston drive as defined in claim 1 further including piston rods on said work piston, recesses in said piston rods, annular chambers surrounding said piston rods, and said recesses in said piston rods communicating with said annular chambers when said piston is at one end of said work chambers. 

